Tires are historically prepared with treads of a rubber composition which is comprised of various elastomers and particularly styrene/butadiene copolymer and a minor amount of cis 1,4-polybutadiene rubber.
Tire tread rubber compositions conventionally contain particulate reinforcing fillers which are normally carbon black and/or aggregates of precipitated silica. Such reinforcement fillers are will known to those having skill in such art.
When precipitated silica is used as a reinforcing filler, its reinforcing effect for the elastomer(s) is usually enhanced with the aid of a coupling agent which contains a moiety which is reactive with hydroxyl groups (e.g. silanol groups) contained on the surface of the precipitated silica and another moiety which is interactive with the elastomer(s), particularly with diene-based elastomers. Such use of coupling agents for precipitated silica aggregates is well known to those having skill in such art.
Sometimes, functionalized elastomers are taught for use with precipitated silicas.
For example, in U.S. Pat. No. 6,013,718, it has been proposed to provide a rubber composition including a functionalized diene polymer and silica in which the functionalized diene polymer bears a chain end as a silanol functional group or a polysiloxane block which has a silanol end. As a further example, in U.S. Pat. No. 6,071,995 such a proposal is made where a carbon black having silica fixed to its surface is suggested for use with a similar functionalized diene polymer.
In the description of the invention, the term “phr” relates to parts by weight of a particular ingredient per 100 parts by weight of rubber contained in a rubber composition.
The terms “rubber” and “elastomer” are used interchangeably unless otherwise indicated, and the terms “cure” and vulcanize” may be used interchangeably unless otherwise indicated.